1. Field of the Invention
The present invention relates to a positioning control device for controlling the positioning of a head for reading/writing on mediums, a changeable magnetic disc device, and a method for controlling the head, and particularly relates to a positioning control device for controlling positioning of the head for reading/writing on the mediums such as changeable discs etc, a changeable magnetic disc device, and a method for controlling the head.
2. Background Art
One example of conventional positioning device, changeable magnetic disc device, and a head control method is disclosed in Japanese Patent Application, First Application No. Hei 9-198816. The devices control the positioning so that a width W of the magnetic head for reading a burst pattern satisfies the following equation;
P+exe2x89xa6Wxe2x89xa62Pxe2x88x92e
wherein, P represents a pitch of the burst pattern in the radial direction of a disc, and e represents a width of an erasing band in the radial direction of the disc.
However, a problem is encountered that, although the conventional technique can prevent from generating a dead zone in the burst signals, it has not been possible to use a magnetic head having a smaller track width than a half (xc2xd) of the track pitch.
The other problem arises that, when reading a wide track by a narrow head in order to maintain the lower order compatibility, a phenomenon called a limit cycle is likely to be caused in which the head moves back and forth between dead zones located on both sides of the target track center.
The present invention is attained in order to solve the above problems. The object of the present invention is to provide a positioning device of the head position for positioning the head at the center of the dead zones, a changeable magnetic disc device, and a method for controlling the head; wherein the head positioning device is capable of positioning the head at the center of the dead zone, when the head is in the dead zone and when the position between the target track center and the head is separated; thus it is possible to avoid the limit cycle which is the back and forth motion of the head between dead zones located on both sides of the target track center, and it is possible to maintain lower order compatibility.
The first aspect of the present invention provides a positioning control device for controlling positioning of a head that reads and writes on a medium comprising: a phase compensation filter for ensuring stability of positioning of said head that reads and writes the changeable medium; and a position error signal generating device for generating the position error signal for obtaining the position of the dead zone, when the head is in said dead zone in which the change of the position error signal is within a specified range or the position error signal does not change, even if said head moves, based on a combination of burst signals for generating a position error signal which indicates a relative position of said head to said medium.
The second aspect of the present invention provides a positioning control device for controlling positioning of a head that reads and writes on a medium comprising: a phase compensation filter for ensuring the stability of the positioning of said head that reads and writes on the changeable medium; and a position error signal generating device for generating the position error signal for obtaining the position of the dead zone, when the head is in said dead zone in which the change of the position error signal is within a specified range or the position error signal does not change, even if said head moves, based on a combination of the burst signals for generating a position error signal which indicates a relative position of said head to said medium and a track number written on said medium.
The third aspect of the present invention provides a positioning control device according to the first or the second aspect, wherein, if said head is located at a position separated more than a half track from the target track center, the positioning control device determines that the head position is present at the center portion of said dead zone.
The fourth aspect of the present invention provides a positioning control device according to the first or the second aspect, wherein, if said head is located at a position closer than a half track to the target track center, and when the track number of said head changes as a result of obtaining two samples of servo signals, the positioning control device determined that the head position is located at the center region of the dead zone.
The fifth aspect of the present invention provides a positioning control device according to the first or the second aspect, wherein, if said head is located at a position closer than a half track to the target track center, and if the track number of said head does not change as a result of obtaining two samples of servo signals, the positioning control device determines that the head position is located at a position closest to the target track center of the dead zone.
The sixth aspect of the present invention provides a positioning control device comprising a head for reading and writing on the exchangeable medium and a positioning control device according to the first or the second aspect of the present invention.
The seventh aspect of the present invention provides a method of controlling positioning of a head which executes reading and writing on the medium, the method comprises: a phase compensating step for preserving the stability of positioning of the head for reading and writing on the changeable medium; and a position error signal generating step for generating the position error signal for obtaining the position of the dead zone, when the head is in said dead zone in which the change of the position error signal is within a specified range or the position error signal does not change, even if said head moves, based on a combination of burst signals for generating a position error signal which indicates a relative position of said head to said medium.
The eighth aspect of the present invention provides a method of controlling positioning of a head which execute reading and writing on the medium, the method comprises: a phase compensating step for preserving the stability of positioning of the head for reading and writing on the changeable medium; and a position error signal generating step for generating the position error signal for obtaining the position of the dead zone, when the head is in said dead zone in which the change of the position error signal is within a specified range or the position error signal does not change, even if said head moves, based on a combination of burst signals for generating an position error signal which indicates a relative position of said head to said medium and a track number written on said medium.
The ninth aspect of the present invention provides a method of controlling the position of said head according to the seventh aspect, wherein, if said head is located at a position separated by more than a half track from the target track center, the head position is determined to be present at the center portion of said dead zone.
The tenth aspect of the present invention provides a method of controlling the position of the head according to any one of claims 7 and 8, wherein, if said head is located at a position closer than a half track from the target track center, and if the track number of said head does not changes as a result of obtaining two samples of servo signals, the positioning control device determines that the head position is located at a position closest to the target track center of the dead zone.
The eleventh aspect of the present invention provides a method of controlling the position of the head according to any one of claims 7 and 8, wherein, if said head is located at a position closer than a half track to the target track center, and if the track number of said head does not changes as a result of obtaining two samples of servo signals, the positioning control device determines that the head position is located at a position closest to the target track center of the dead zone.